The accurate placement and monitoring of underwater equipment, such as wellheads, manifolds, risers, anchors, Pipeline End Terminations (PLETS), Blow Out Preventors (BOPs), pumps, touch down points, suction piles, chains, slip joints, templates and pipelines is important to ensuring the safe and reliable operation of such equipment. However, the methods available in underwater environments are limited when compared to surface environments. For example, radio frequencies are severely attenuated in underwater environments, making radio frequency based location systems, such as a Global Navigation Satellite System (GNSS) like the U.S. Global Positioning System (GPS) and the now obsolete long range navigation (LORAN) systems, unusable at depth. In addition, conventional land survey techniques, for example using theodolites and measuring tapes, can be limited by limited visibility, and because they typically must be operated directly by a human, which may not be possible or practicable in certain underwater scenarios. As a result, accurately determining the location of equipment and measurements between equipment in underwater environments during installation and survey operations is challenging.
Conventional techniques for determining a location underwater can include the use of inertial navigation units (INUs). In addition, arrays of acoustic transducers having known locations can be used for determining location within or near the array. Although acoustic techniques can provide relative bearing and distance information, the accuracy and precision of such systems is relatively low. For example, relative locations can at best be determined with an accuracy of several centimeters.
More precise location information can be obtained using active optical techniques. For instance, underwater lidar systems are available that can provide relative location with a precision of several millimeters or less. However, such systems can suffer from limited operational range, particularly in turbid water conditions.
Accordingly, it would be desirable to provide systems and methods that allowed for reliable and precise determination of location in underwater environments.